1. Field of the Invention
The present invention relates to a method for correcting stereoscopic images in which stereoscopic images are corrected, a stereoscopic display device and a stereoscopic image generating device using the method for correcting stereoscopic images.
2. Description of the Background Art
Conventionally, stereoscopic devices adopting various systems that enable stereoscopic viewing with naked eyes and that use a special pair of eyeglasses are put to practical use. A method for enabling stereoscopic viewing with naked eyes includes holography, a method for controlling light reaching viewer's right and let eyes using a parallax barrier or a lenticular lens provided to a surface of a liquid crystal panel, and a method for controlling light reaching viewer's right and left eyes in a time division system by combining backlight having directivity of outgoing light (hereinafter, directional backlight) and a liquid crystal panel of a field sequential system.
On the other hand, the method using a special pair of eyeglasses includes a method for providing polarization plates having a different polarizing direction between right and left eyeglasses and viewing images whose polarization is different and separating the right and left images, and a method for controlling light reaching viewer's right and left eyes in a time division system by combining shutter eyeglasses with a liquid crystal panel of field sequential system.
In many stereoscopic display devices adopting the above systems, a stereoscopic crosstalk (hereinafter, crosstalk) caused by various factors, which deteriorates visibility of stereoscopic images, is present. The crosstalk means that right and left parallax images are mixed (seen) with a right image and a left image. When the crosstalk is present, an image is mixed on a portion where the image is not originally seen, and a false image (hereinafter, a ghost) is viewed, thereby disturbing stereoscopic viewing and increasing tired feeling of the stereoscopic viewing.
An example of a stereoscopic display device, for combining directional backlight with a liquid crystal panel and providing stereoscopic display that enables stereoscopic viewing with naked eyes, is a stereoscopic display device disclosed in Japanese Patent Application Laid-Open No. 2001-66547 (FIG. 1). This stereoscopic display device has two light sources for focusing light to viewer's right and left eyes, turns on the light source for right eye in synchronization with display of a parallax image for right eye on the liquid crystal panel, turns on the light source for left eye in synchronization with display of a parallax image for left eye, and displays the right and left parallax images alternatively to display a stereoscopic image.
Factors of the crosstalk occurring in the stereoscopic display device in Japanese Patent Application Laid-Open No. 2001-66547 include two components. One of the components is a component, whose luminance of light emitted to a right-eye direction at the time when stray light is generated in backlight and a liquid crystal panel and the light source for left eye is turned on does not completely become zero (in the case of the light source for right eye, component whose luminance of light emitted to a left-eye direction does not completely become zero). The other component is a component that is generated by a response delay of the liquid crystal panel because the liquid crystal panel is driven in time division.
Since the component caused by the stray light in the factors of the crosstalk hardly changes even when the liquid crystal panel provides any display, a crosstalk amount simply becomes a value obtained by multiplying gradation luminance on an opposite side (namely, a parallax image for right eye shown at the time of display of a parallax image for left eye) by a constant. A signal processing method relating to crosstalk elimination/correction in such a case is disclosed (for example, see Japanese Patent Application. Laid-Open No. 2001-298754).
Japanese Patent Application Laid-Open No. 2001-298754 discloses a crosstalk correcting method in the case where the crosstalk amount is simply a constant-times larger, and this method cannot cope with the case where a complicated crosstalk amount such as liquid crystal delay occurs. Since the lowest luminance of an input image is raised to a level of a maximum crosstalk amount, entire contrast is remarkably deteriorated, and thus display quality is deteriorated.